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Our automotive experts have put together the following information about the P2603 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P2603 code.

OBD II Fault Code

  • OBD II P2603

    OBD-II Code Powertrain Control Module (PCM) failure is defined as a Coolant Pump "A" Control Circuit High

    To Coolant Heat Storage (CHS) system allows the gas engine on a hybrid vehicle to warm up before the engine is actually started. This allows the gas engine to use less fuel when it is started. The CHS system uses a dedicated tank to store hot coolant. Before the engine is started, the electronically controlled engine water pump circulates this already hot coolant through the engine. If the engine computer (PCM) detects the electric pump is not operating properly, the PCM will set code P2603.

    Common Problems That Trigger the P2603 Code

    • Coolant Heat Storage (CHS) water pump failure
    • Coolant Heat Storage (CHS) water pump relay
    • Powertrain Control Module (PCM) failure
    • Wiring issue
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